Green synthesis of luminescent La-MOF nanoparticle from waste poly(ethylene terephthalate) for high-performance in Fe(III) detection

Developing luminescent metal–organic frameworks (MOFs) capable of high-efficiency Fe³⁺ sensing has aroused great attraction in the fields of biology, chemistry, etc. However, previous solvothermal methods are limited by organic solvent usage, time consuming, high pressure, and high-energy consumption. Herein, we propose the waste-to-MOF strategy towards the scale-up production of La-MOF nanoparticles through the ball milling of recycled poly(ethylene terephthalate) (PET) bottles and La(NO₃)₃⋅6H₂O. PET goes on alkaline hydrolysis to form 1,4-benzenedicarboxylic acid sodium salt (Na₂BDC) and ethylene glycol by ball milling. Subsequently, BDC reacts with La³⁺ to form La-MOF. The as-prepared La-MOF crystal nanoparticles possess a rod-like morphology with the size of few hundred nanometers. Additionally, La-MOF nanoparticles display high selectivity and sensitivity for Fe³⁺ detection. The quenching constant and limit of detection are 5.29 × 10³ (mol·L⁻¹)⁻¹ and 0.147 μmol·L⁻¹, respectively, thus surpassing many advanced Fe³⁺ sensors. According to the result of density functional theory, the high Fe³⁺ detection performance of La-MOF is related to the complexing of Fe³⁺ with La-MOF, which leads to the gradual dissociation of the coordination bond between terephthalic acid and La³⁺. It is anticipated that the mechanochemistry milling-based waste-to-MOF strategy provides a new platform for the massive production of functional MOFs in a green manner.